<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>课后练习-2</title>
<link href="课后练习-2.css" rel="stylesheet" type="text/css">
</head>
<body>
<div id="box">
<div class="content"></div>
</div>
</body>
</html>
@charset "utf-8";
/* CSS Document */
#box {width: 344px;height: 389px; background: url(img2/background.png);}
.content { width:244px; height:289px; background-color:#FF0004; padding:50px;}
子元素设置背景颜色，父元素也跟着改变是什么原因？
侠客岛的含笑